const Crypto = {};
(function () {
    var base64map = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

    // Crypto utilities
    var util = (Crypto.util = {
        // Bit-wise rotate left
        rotl: function (n, b) {
            return (n << b) | (n >>> (32 - b));
        },
        // Bit-wise rotate right
        rotr: function (n, b) {
            return (n << (32 - b)) | (n >>> b);
        },
        // Swap big-endian to little-endian and vice versa
        endian: function (n) {
            // If number given, swap endian
            if (n.constructor == Number) {
                return (util.rotl(n, 8) & 16711935) | (util.rotl(n, 24) & 4278255360);
            }

            // Else, assume array and swap all items
            for (var i = 0; i < n.length; i++) {
                n[i] = util.endian(n[i]);
            }
            return n;
        },
        // Generate an array of any length of random bytes
        randomBytes: function (n) {
            for (var bytes = []; n > 0; n--) {
                bytes.push(Math.floor(Math.random() * 256));
            }
            return bytes;
        },
        // Convert a string to a byte array
        stringToBytes: function (str) {
            var bytes = [];
            for (var i = 0; i < str.length; i++) {
                bytes.push(str.charCodeAt(i));
            }
            return bytes;
        },
        // Convert a byte array to a string
        bytesToString: function (bytes) {
            var str = [];
            for (var i = 0; i < bytes.length; i++) {
                str.push(String.fromCharCode(bytes[i]));
            }
            return str.join('');
        },
        // Convert a string to big-endian 32-bit words
        stringToWords: function (str) {
            var words = [];
            for (var c = 0, b = 0; c < str.length; c++, b += 8) {
                words[b >>> 5] |= str.charCodeAt(c) << (24 - (b % 32));
            }
            return words;
        },
        // Convert a byte array to big-endian 32-bits words
        bytesToWords: function (bytes) {
            var words = [];
            for (var i = 0, b = 0; i < bytes.length; i++, b += 8) {
                words[b >>> 5] |= bytes[i] << (24 - (b % 32));
            }
            return words;
        },
        // Convert big-endian 32-bit words to a byte array
        wordsToBytes: function (words) {
            var bytes = [];
            for (var b = 0; b < words.length * 32; b += 8) {
                bytes.push((words[b >>> 5] >>> (24 - (b % 32))) & 255);
            }
            return bytes;
        },
        // Convert a byte array to a hex string
        bytesToHex: function (bytes) {
            var hex = [];
            for (var i = 0; i < bytes.length; i++) {
                hex.push((bytes[i] >>> 4).toString(16));
                hex.push((bytes[i] & 15).toString(16));
            }
            return hex.join('');
        },
        // Convert a hex string to a byte array
        hexToBytes: function (hex) {
            var bytes = [];
            for (var c = 0; c < hex.length; c += 2) {
                bytes.push(parseInt(hex.substr(c, 2), 16));
            }
            return bytes;
        },
        // Convert a byte array to a base-64 string
        bytesToBase64: function (bytes) {
            // Use browser-native function if it exists
            if (typeof btoa == 'function') {
                return btoa(util.bytesToString(bytes));
            }
            var base64 = [];
            var overflow;
            for (var i = 0; i < bytes.length; i++) {
                switch (i % 3) {
                    case 0:
                        base64.push(base64map.charAt(bytes[i] >>> 2));
                        overflow = (bytes[i] & 3) << 4;
                        break;
                    case 1:
                        base64.push(base64map.charAt(overflow | (bytes[i] >>> 4)));
                        overflow = (bytes[i] & 15) << 2;
                        break;
                    case 2:
                        base64.push(base64map.charAt(overflow | (bytes[i] >>> 6)));
                        base64.push(base64map.charAt(bytes[i] & 63));
                        overflow = -1;
                }
            }

            // Encode overflow bits, if there are any
            if (overflow != undefined && overflow != -1) {
                base64.push(base64map.charAt(overflow));
            }

            // Add padding
            while (base64.length % 4 != 0) base64.push('=');
            return base64.join('');
        },
        // Convert a base-64 string to a byte array
        base64ToBytes: function (base64) {
            // Use browser-native function if it exists
            if (typeof atob == 'function') {
                return util.stringToBytes(atob(base64));
            }

            // Remove non-base-64 characters
            base64 = base64.replace(/[^A-Z0-9+\/]/gi, '');
            var bytes = [];
            for (var i = 0; i < base64.length; i++) {
                switch (i % 4) {
                    case 1:
                        bytes.push((base64map.indexOf(base64.charAt(i - 1)) << 2) | (base64map.indexOf(base64.charAt(i)) >>> 4));
                        break;
                    case 2:
                        bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 15) << 4) | (base64map.indexOf(base64.charAt(i)) >>> 2));
                        break;
                    case 3:
                        bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 3) << 6) | base64map.indexOf(base64.charAt(i)));
                        break;
                }
            }
            return bytes;
        }
    });

    // Crypto mode namespace
    Crypto.mode = {};
})();
module.exports = Crypto;
